22
Trip Characteristics — MicroVersaTrip Plus™ and PM™
Defeatable Ground-Fault Protection (Optional) —
Not UL Listed
A defeatable ground-fault function is offered for users who
want the ability to enable or disable ground-fault protection
depending on special circumstances. When this type of
ground-fault protection is ordered, in addition to the nor-
mal ground-fault settings, the user can disable ground-fault
protection during programming by setting the delay to OFF.
Switchable Short Time or Instantaneous OR Switchable Short
Time or Instantaneous and Ground-Fault Protection (Optional) –
Switchable Ground Fault Not UL Listed
Special breaker applications may require the ability to selec-
tively enable and disable the short circuit protection and/or
ground fault protection of the breaker. Switchable short
time or instantaneous allows either the short time function
or the instantaneous function to be disabled for use in
unique situations such as a breaker functioning as a spare
for several feeders with different trip characteristics. Both
short time and instantaneous functions can be enabled but
both cannot be disabled. Switchable ground fault protection
is similar to the defeatable ground fault function in that it
can be enabled or disabled via the ground fault delay setting.
Zone Selective Interlocking (Optional)
Traditional means of obtaining selectivity between main and
feeder breakers is to set the furthest downstream device with
the lowest time delays, and increase time delays of upstream
devices. The disadvantage of this is that upstream portions
of the system must endure high values of fault current until
time-out occurs.
Breakers equipped with MicroVersaTrip Plus™ or
MicroVersaTrip PM™ trip units can provide improved
protection to zones between breakers through the use of
Zone Selective Interlocking. When a downstream breaker
(feeder) detects a fault, it signals the upstream device
(main) to shift to its preset time delay band, allowing the
downstream device to clear the fault while the upstream
device provides backup protection. If a fault occurs between
two breakers equipped with zone selective interlocking, the
upstream breaker would clear the fault on the minimum
delay band because it receives no interlock signal from a
downstream breaker, thus minimizing the duration that
the fault would exist before being cleared.
Zone selective interlocking is available for either ground
fault only or both ground-fault and short-time functions.
The zone selective interlocking feature requires a zone
selective interlock module (ZSIM) for each zone. The
module is an intermediate control device used between
upstream and downstream circuit breaker to communicate
with the short-time and ground-fault zone selective interlock
functions of the MicroVersaTrip Plus and MicroVersaTrip
PM trip units. The module (Cat. No. TIM1) requires
120/208/240 Vac control power, 15 VA maximum.
The module can communicate with up to 30 downstream
breakers and up to 6 upstream breakers provided all
breakers share the same zone.
Multi-zone selective interlocking
Operation Of MicroVersaTrip PM Trip Units
MicroVersaTrip PM trip units add communications
capability with remote host computers and the GE POWER
LEADER™ Power Management System. In addition, the
user can choose to add metering with or without additional
protective relaying. In the block diagram (page 23) of the
MicroVersaTrip PM trip unit, note that there are two addi-
tional sets of inputs — voltage inputs from each phase and
a 24 Vdc input from an external power supply. Additionally,
there is a communications input/output link to the POWER
LEADER system.
Voltage Inputs
Voltage Inputs to the MicroVersaTrip PM trip unit are
required for both metering and protective relays. Voltage
inputs require three delta or wye-connected potential
transformers with 120 Vac secondaries, and an external
voltage module that further conditions the voltage signals
for use by the trip units microprocessor. A single set of
external voltage modules can serve the requirements of
up to 16 trip units.
Bus
Zone 0 CB1
Zone 1 CB2
Zone 2 CB3
Zone 3 CB4
Motor
Source
L1
L2
ZSIM No.1
ZSIM No.2
M
V
T
M
V
T
M
V
T
M
V
T
M
V
T
“Output” from Trip unit
“Input” to Trip unit
ZSIM No.1
Downstream
Connections
Upstr eam
Connections
Wiring
ZSIM No.3
